Daily rations,diel feeding activity and distribution of age-0 brook charr,Salvelinus fontinalis,in two subarctic streams

Synopsis Diel variations in the stomach content weight of age-0 brook charr indicate that they fed primarily during the day in Matamek River and Rivière à la Truite, Québec. Age-0 charr in both rivers moved close to the shore at night. The mean weight of stomach contents in Rivière à la Truite was highest at the end of the daylight period, whereas in the Matamek River stomach content weights maintained maximum level during most of the day, except in August when high water temperatures reduced food intake. Daily rations were estimated at 5.09 and 4.09% body weight for charr from Rivière à la Truite in July and August, respectively. In the Matamek River, estimates were 7.13, 9.75, and 1.27%, in June, July, and August, respectively. Charr from Matamek River had a higher instantaneous growth rate than charr in Rivière à la Truite (3.96 versus 2.72% body weight per day) and were significantly heavier by mid-August. Differences observed between populations in daily rations and growth rates were attributed mainly to differences in water temperature regimes.